Will Additive Manufacturing Play a Major Role in Aircraft Production?

Will additive manufacturing become an accepted and widely used process in aircraft production?

One point of view says the answer is probably yes. Military aircraft maker Lockheed Martin Aeronautics, for example, is working to advance additive manufacturing—the technology of forming parts by laying down material in precise layers. The company is experimenting with aircraft structural components produced through a production additive process, and it foresees considerable improvements in aircraft performance and cost as a result of one day making significant parts of the aircraft with this technology.

However, from another point of view, additive manufacturing is already widely used in aircraft production. After all, part of manufacturing a plane is manufacturing the tooling used to make that plane. Lockheed Martin’s Forth Worth, Texas, production facility currently uses 5,000 jigs and fixtures produced through additive manufacturing. The plant has 18 additive machines from various makers of this technology, and these machines are in use 70 percent of the time producing new or replacement production tooling. When it comes to building this tooling, additive manufacturing is not a leading-edge possibility, but a long-established fact.

This very experience with making and relying on engineered tooling produced additively contributes to the confidence of Lockheed Martin leaders that components of this company’s planes—even flight-critical parts—will eventually be made through additive processes. I had the chance to speak about this with Joseph Rappisi, the company’s VP of aeronautics production operations, and Don Kinard, Ph.D., senior fellow with the company.

Both men make it clear that additive manufacturing is not yet ready for flight-critical parts, and likely will not be ready soon. Comparing today’s additive manufacturing technology with what that technology might plausibly deliver in the future is, in Mr. Rappisi’s words, a matter of comparing “the state of the art versus the art of the possible.” In spite of its limitations today, however, additive manufacturing of aircraft parts is seen as a real possibility, and the company is exploring the potential this possibility might hold not only for its production processes, but also for the design of its planes.

Part of the potential is aircraft that are dramatically less expensive to operate. A plane with major structural members produced through additive manufacturing would be a plane with far fewer fasteners, because additive’s ability to generate complex structures means that structures that are assemblies today might be grown as a single piece. Fewer fasteners means less weight, reducing fuel cost, and also fewer stress points, likely extending the life of the plane. An additively manufactured plane would thus be one with a much lower total cost of ownership.

But again, we’re not there yet, Dr. Kinard says. Some of the requirements are being met. Additive manufacturing technology with the size and speed for mass production of aircraft components is now achievable, for example. Lockheed Martin is experimenting with wing spars and related parts made through electron beam welding, an additive process capable of laying down material quickly. But in terms of metallurgy and material consistency, the seemingly dense metal parts made from this process are not currently capable of passing Lockheed Martin’s engineering requirements, let alone achieving government certification for assembly into a plane.

Porosity is an issue, Dr. Kinard says. The consistency of the electron-beam-welded parts is superior to that of a casting, and could replace a cast part, but an aircraft’s fracture-critical members are not made through casting. “We need to get to the point where we can treat this material like plate or forging,” he says.

Another issue is the cost of the process itself. Even if additive manufacturing does achieve the ability to create forged-like parts, it won’t necessarily do so in a way that is cost-effective compared to forging. Like a forging, the additive part will still require machining to achieve final tolerances. In addition, it might always be the case that additive parts will require heat treating, or hot isostatic pressing (HIP) in the case of additive parts made from powder. That is why he says, “We might discover that additive is cost-effective only for components that can’t be made any other way.”

The ultimate answer to questions such as these is impossible to predict, because both the capabilities and the economics of additive manufacturing are still advancing rapidly. Makers of additive machines are working closely with Lockheed Martin to develop a machine that meets the company’s requirements for this technology, in part because achieving full acceptance in the production of critical aircraft parts would mean the technology was proven and had essentially arrived.

Dr. Kinard says he believes he sees similarity between additive technology and the advance of composites in aircraft manufacturing. His own career in aircraft manufacturing spans 30 years. At the beginning of that career, when aircraft composites were new, he says he might have imagined that we would one day see an all-composites plane. Today, that notion would seem fanciful, yet composites are now accepted and in widespread use in aircraft production. During those 30 years, while composites technology was advancing, industry also figured out where composites both do and do not make sense.

Notably, he says one of the keys to the acceptance of composites was technology for inspecting and certifying parts made with these materials. For additive, that development is still needed. Rather than inspecting the final part, he believes inspection in additive manufacturing will ultimately take the form of monitoring each layer as it is built.

The technology is moving more quickly than composites did, he says. The full arc to additive manufacturing’s maturity likely will not take another 30 years. But there will be a delay. Even after achieving both the capability and the opportunity to introduce an additively fabricated part, getting certification for a primary component made in such a novel way could take an additional 3-5 years.

That delay is good, says Mr. Rappisi. The life of a war fighter, a U.S. military pilot, depends on the integrity of the plane. Thus, it’s fitting that there is redundancy and assurance built into the process for validating that this integrity is there.

“We never forget who we’re working for,” Mr. Rappisi says. Reducing the life cycle cost of the plane is a valuable objective, he notes, but it is not the most important goal.

We are not yet close to the day when the aircraft itself will be made through additive manufacturing, but tooling used to make the aircraft has been produced this way for years. F-35 image in the previous photo courtesy Lockheed Martin.

Experimental F-35 components have been produced through additive manufacturing, such as the flap spar seen here. Once the part is machined, it looks identical to a part manufactured conventionally. However, the metallurgy and material consistency is a different matter, and it is here that Lockheed Martin and additive manufacturing technology suppliers are working toward improvements.

Even without making flight-critical parts, additive manufacturing is already a significant part of production. The company’s Forth Worth production facility currently uses 5,000 jigs and fixtures made on 18 different additive machines in the facility, such as the one seen here.

This article is reprinted with permission from Modern Machine Shop Magazine, and is protected under U.S. and international copyright laws. Modern Machine Shop Magazine is protected under U.S. and international copyright laws. Before reproducing anything from this Web site, call Gardner Business Media, Inc. (513) 527-8800.

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